Spaces where occupancy density and consequently the potential for human pathogen spread is high, or where processes create air pollutants such as dust, gases are prime candidates for local ventilation entrainment and recirculation, filtration, air purification and air cleaning. Such spaces where occupant generated pathogens and irritants are a concern include aircraft passenger cabins, conference rooms, trains, trains, buses, subways, submarines, street cars, cars, classrooms, theaters, auditoriums and animal feed lots/barns. Moving sufficient air through central heating, ventilation and air-conditioning (HVAC) systems to dilute these air contaminants to safe levels can be costly, as can the extensive use of portable air cleaners.
Air contaminants such as chemicals and pathogenic organisms, and ventilation air supply thermal and humidity gradients, particularly in high occupancy enclosed spaces such as in transportation vehicles, can present health and comfort concerns due to the limitations of existing ventilation systems using conventional air flow controllers and outlet diffusers to deliver air cleaned centrally. Existing systems may filter, purify and/or clean the air delivered and thus provide a limited amount of local dilution of air contaminants but they have limitations: pathogens and air contaminants, for example, can still be circulated locally by the airflow patterns introduced by the diffusers, by occupant movement and other forces, travelling laterally between occupants before being returned to a central air cleaner and conditioner system.
Ventilation air and air curtain air boundary layers can entrain contaminants (including dust and insects), causing them to enter the occupant breathing zone or space being protected.
In buildings, aircraft, trains, buses and the like, or other environments, ventilation air is typically provided by a central environmental control system (ECS) or heating, ventilation and air-conditioning (HVAC) system. The system typically delivers a supply of thermally conditioned and filtered, purified and/or cleaned air through ducting to room air diffusers and in the case of aircraft and other passenger vehicles, to cabin air diffusers and gaspers or personal air outlets (PAOs).
One problem lies in part in the entrainment into the ventilation air of localized air pathogens, dust, odours, or insects as it passes on its way from the diffusers to the occupant breathing zones.
Ventilation systems do not adequately address direct person-to-person air contaminant and pathogen spread. Prior flow controller and diffuser designs do not filter out air contaminants in the local space, which is where many air contaminants are generated. These pathogens, dust and odours are drawn into the air supply as it passes to the occupant-breathing zone by the airflow turbulent boundary layer. Hence, even personal ventilation devices such as gaspers can actually increase rather than decrease the spread of airborne disease.
Existing ventilation systems also suffer from other drawbacks and there is a need for improved and more effective ventilation systems and components thereof.
The present inventor has previously described in PCT patent application no PCT/CA2007/000889, devices which when used with an aircraft gasper or Personal Air Outlet, takes advantage of the air supply momentum imparted by the existing ventilation system to entrain local air, filter and clean it as desired, provide a supply of filtered, purified and/or cleaned air to passengers and crew, mitigate against air contaminants emanating from neighbouring occupants and equipment, and improve local thermal conditioning and comfort.